1. Field of the Invention
The present invention relates to steam nozzles used to pre-heat feed water for steam based heating systems, and more particularly to a detector for detecting erosion of the steam nozzle so that replacement can be effected before damage can result.
2. Description of the Prior Art
In steam based heating systems, water is heated to steam and the steam is then delivered to various radiators of the steam pipe circuit for providing heating of a building, such as for example a school. In this regard, a boiler is used to heat feed water to steam. Cold feed water cannot be directly added to the boiler because if it mixed with the very hot environment inside the boiler, the result could be disastrous. Accordingly, feed water is pre-heated before being introduced into the boiler.
Pre-heating of feed water is carried-out by introducing a controlled flow of steam into the feed water of a feed water vessel via a feed water steam nozzle. The feed water steam nozzle has a number (usually four) of mutually spaced hole rows along its length (which is more-or-less about forty-five inches), each hole row having a plurality of regularly spaced apart (about one inch) holes (about one-quarter inch in diameter) along its length. Although made of heavy gauge metal (schedule 80, having a inner diameter of about two inches and an outer diameter of about two and one-quarter inches), the feed water steam nozzle is subject to erosion over its useful life because of the extreme steam pressures built-up inside. Indeed, the end of the feed water steam nozzle is capped at its distal end, so that steam entering into the feed water steam nozzle encounters returning steam from the distal end more-or-less around the mid-section of the feed water steam nozzle. Accordingly, the metal defining the holes slowly erodes away, the rate of erosion being highest at the mid-section portion of the feed water steam nozzle.
As the holes enlarge, the rate of steam release into the feed water is less controlled, and steam pulsations will occur. The result of these pulsations is "hammering", wherein the feed water steam nozzle shakes violently. When the feed water gets warmer, the "hammering" subsides, and the boiler operator, who has no exact knowledge of the condition of the feed water steam nozzle, might assume the problem was transitory and not the result of erosion. However, in all likelihood the steam water feed nozzle is dangerously eroded and presently in Hire need of replacement before major damage to the boiler system is sustained. However, boiler operators are reluctant to drain the feed water vessel and then go through the rigor of inspection on only the chance that the feed water steam nozzle is eroded.
Accordingly, it would be very beneficial if a definite indication of feed water steam nozzle erosion could be provided, especially before "hammering" occurs.